Method of preventing landslides



Patented May 9, 1m

- Victor a. Bndersby, Lafayette, calm, anchorto Shell DevelopmentCompany, San Francisco, Calm, a corporation of Delaware No ApplicationApril 28, 1943, Serial No. 484,945

The present invention pertains to methods of preventing landslides andrelates particularly to methods of treating underground strata'ofabsorbent clays, particularly bentonitic clays, to prevent theirbecoming wet to the point of formins slurries and causing landslides.

Since water absorption "by bentonitic clays is quite rapid since themechanical strength of bentonitic clays drops'oif sharply at a criticalwater saturation, water absorption by bentonitic 1 strata often causessudden large shifts of overly-o ing earth masses without warning. Water2111- sorption by other absorbent clays which form aqueous slurries mayalso cause landslides, but -.these are less serious to combat becausethe memore gradually with increasing water saturation than does that ofbentonitic strata and thus the resulting landslide generally moves moreslow y or in smaller earth masses or discontinuously for v shorterdistance. Therefore, although the present method may be used to treat,in general, absorbent clay strata which are potential causes oflandslides, the method of the present invention is particularlyapplicable to the treatment of bentonitic strata for preventingunheralded and sudden landslides of disastrous proportions. For sake ofsimplicity only, however, the invention is described hereinbelow inrelation to its particular application to bentonitic strata. 4 Thepreventionof landslides is particularly important in the construction-ordams, foundations forheavy structures and the like. Herebefore. asphaltemulsions have been used to solidify soils in such areas. It has'nowbeen found that strata of bentonite and bentonitic clays in'mountainsare frequently subject to the action of infiltrat ing water and thuscause a great number of landslides. The water entering the bentonitic'strata results in the swelling of the bentoniteor bentonitic clay andreduction of the viscosity approaching that of a"slun'y, which then maycause the sudden downward movement of the overlying mass to a morestable position. However, benf tonitic clays have such a lowpermeability due to compaction or sweHing thereof after -absorp-' areforced into the more permeable surrounding strata leaving the bentoniticstratum or seam still relatively. free toabsorb more water until aslurry of the bentonite is formed, wherebyja slide occurs. to andpreferably a liquid petroleun distillate having v ehanlca-lstren th ofsuch clays decreases much A 13 Claims. (CL 81-36) It'is an object ofthis invention to provide a method of preventinglandslides due toabsorption of water by absorbent clay strata by treating said stratawith a material which may be easily inlected deeply into said strata andwhich is capable of preventing absorption of water by the bentonite. IIt is a particular object of this invention to provide a method ofpreventing landslides due to absorption or water by bentonitic claystrata by treating said bentonitic strata with a material which may beeasily injected deeply into said.

strata-and which is capable of preventing absorption of water by thebentonite.

Insome particular cases, such asoin constructing dams, it is found bycore-drilling (or other suitable subsurface investigation) that adesired I earth cut. or excavation cannot be made without danger ofslides because-of an underlying bentonitic strata containing a certainamount of ab--' sorbed water, which, although perhaps not suflicient tocause a slide in itself, would result in an incipiently dangerouscondition. If the excavation or out were made in earth under thiscondition, a serious landslide would in all probability occur upon thefurther absorption of a slight amount of water from even light rain orsomtimes foggy weather.

Therefore, a special object of this invention is to provide a method ofpreventing landslides comprising the steps of first treating suchwater-wet bentonitic strata to remove at least part of the water fromsaid strata and thereby to reduce the swelling of the bentonite with anagent, which itself does not cause appreciable swelling of the ventfurther' entrance of water, all prior to making the desired earth cut,den or other earth 40 removal operation which'would otherwisecause alandslide under untreated soil conditions.

According to the present invention. landslides caused by the formationof bentonitic slurries in underground bentonitic strata due toabsorptionof water thereby, are prevented by introducing into said strata a lowviscosity mineral oil containin'g an'oleophiiic cation active wettingagent.

By 10w viscositymineral oil is meant a mineral oil having a viscositylow enough to allow the oil to flow readily under the operatinghydrostatic pressure head-into the desired bentonitic strata. InGeneral, mineral oils having viscosities from about 50 to 500'secondsSaybolt Universal (approximately Oflito IOJWenGPO SeS) at E,

, monium compounds and the analogous phosphorous, sulfur, arsenic,antimony, etc.,=- compounds; their salts; their derivatives such aschloro g hydroxo-sulfoether, ester, etc.; primary, secondary or tertiarymono or poly amines and their derivatives, etc. Both these groups ofcompounds include aliphatic, cyclic,*nuclear or extranuclear compounds,preferably containing at least one aliphatic saturated hydrocarbonvented.

of 8, and preferably, 10 or more carbon atoms. Such compounds arerepresented by trimethyl cetyl ammonium chloride, lauryl pyridiniumchloride, the quatemary salt of diethyl aminoethyi oleyl amide, laurylquinaldinium bromide, 7

go suchas "wax amines and it was found that triethyi hexadecylphosphonium bromide, the ternary sulfonium compound: methyl ethyl cetylsulfonium methyl sulfate, methyl stearyl amine, chloro palmityl amine,stearic ester of ethanol amine, etc. For additional agents and theirmethods of manufacture see, for example, Dohse et al., U. S. Patent2,191,295.

Cationic wetting agents, which were found to be particularly suitable,may be obtained from wax by chlorination and ammonolysis, the formerbeing conducted at a temperature of about is reached, and the la 'terstep taking=place at about 150 C. in the resence of a solvent such asalcohol. In the following description these cation active compounds willbe referred to as paraffin wax amines," or. wax amines."

A similar group of amines, likewise highly effective for the purposes ofthe present. invention, are the alpha branched aliphatic primary amines,

' having more than 12 carbon atoms, which are derived from aliphaticmono-oleflns by hydrochlorination and .ammonolysis, and will be referredto as "alpha methyl amine" or "alpha amine" for short.

The range of concentrationfof cationic wetting agent in the lowviscosity oil is from about 2% to 2% or more, and preferably from to 1%depending on the nature of the wetting agent' and the oil used. Forexample, the miniquire a certain amount ofeifectiveness when used incombination .with'cationic compounds, although this effectivenessremains in general :lbelow that of cationic compounds alone.

As illustrative only of a preferred embodiment ofthe method ofthe'present invention, the following ,example is .given. ".In theconstruction of a dam it was necessary to remove a large section ofearth forming the wall qfa canyon -in which the dam was to be placed.Pri r t the earth'removal operations a careful core drllling into thecanyon wall revealed a relatively thin stratum ofbentonite, whichoutcropped fur- .ther up the canyon .It the dam were constructed withouttreating said bentonite stratum or seam and the water backed upby thedam were allowed to rise to the point where it could enter the bentoniteseam outcropping, a dangerous landslide and loss of the dam wouldprobably occur.

However, according'to the present invention, if a quantity oflowviscosity gas-oil containing 0.5% of paraflin wax amines" is introducedinto 10 the bentonite seam-through the core drilling borehole and otherboreholes, some into the hentonite outcropping, then,entran ce of waterinto the bentonite'seam and the formation of a hen-- tonite slurry witha resulting landslide is pre- In laboratory tests core samples andcolumns of packed bentonite and bentonitic clays were treated with lowviscosity mineral oils, such as gas-oil, containing cationactive wettingagents,

columns or core samples. No further swelling 25 of the'bentonite. norformation of slurries occurred.

Results of tests showing the eflect of the use of gas-oil containingcationic agents upon swollen bentonite under conditions simulatingnatm'e are reported in the table below. In these tests, a 110 C. until achlorine content of about 30% pressure injection apparatus comprising asteel block with a chamber 1 x 1.5 x 30 cm. and fitted with glasswindows and openings at each end .was used. Dry bentonite was packed inthe chamber and water forced in under 100 lbs. per

sq. in. After allowing sufficient time for the complete hydration of thebentonite, gas-oil with and without cationic compounds was forcedthrough the sample followed by water under 100 40 lbs. per sq. in.

Experiment number Oilused Gas-oil alone. 1 perniiln l "per-min ammar."in 73111111 in gu-o gu-o Water flow before 180 ccJhr. aft- 180 ccJhr.aft- 180 cc./hr. after treatment. er llfi ghrs. er v18 hrs. igghmswellswon flow 35 cc. in 10 0.4 mm. m nee hr. for

min. this. r this. Water flow titer 45 for None 34 cc./hr. (or 34treatment with 1st 0.4 hmmca/hr. oil. eeJhr. iorli for 1 hrs 0 hrs.ccJhr. 'for 5 The above results illustrate that the use of a lowviscosity mineral oil containing a cationic compormd on wet bentoniteproduces an effective .plug to the continued passage of water. This toprevention of entrance of water into the ben-- tonitic'material andabsorption of water thereby dry. In fact, it was found that water up toa 06 certain amount, depending on the nature of the bentonitic material,added to its mechanical in-the case of bentonite and to a lesser extentin hentonitic clays, the decrease in the mechanical strength of thebentonitic material becomes very rapid with a small increase Y in thewater content over certain critical ranges. In cases wherein the watercontent of the hentonitic material of an underlying inclined stratum (6is-in or near this incipiently dangerous condition,

the bentonitic stratum with a water soluble, substantially non-polarsolvent, i.'e. a solvent having a very small dipole moment or none atall. A most convenient-solvent is dioxane. Other suitable substances,some of which may have to be used in solutions of benzene, toluene,xylenes, mesitylene, etc., because of their relatively high meltingpoints, include diethylene diamine (piperazine) pyrazine, morpholine,1,4-cyclohexane dione. 1,4-cyclohexane diol, etc.

For example, in a preferred application of the present invention tobentonitic seams containing incipiently dangerous amounts of water, saidbentonitic seam is first treated with dioxane to remove at least a partof the water contained in said seam. The dioxane may be injected intoand withdrawn from the seam in one large treatment or in severaltreatments of smaller volumes. Thereafter, a suitable quantity ofmineral oil containing a cationic surface-active agent is injected intothe bentonitic seam, whereby the heneficial result of the presentinvention, namely, the prevention of landslides, is obtained.

I claim as my invention:

1. A method of preventing landslides water absorption by undergroundbentonitic strata comprising the step of injecting into said strata alow viscosity mineral oil containing a small amount of an oleophilicsurface cation active wetting agent.

a 2. A method "of preventing landslides due to water absorption byunderground bentonitic strata comprising the step of injecting into saidstrata a low viscosity mineral oil containing a small amount of both anoleophilic surface cation active wetting agent and an anion active com;pound.

3. A method of preventing water absorptionby underground absorbent claystrata comprising the step of injecting into said strata a low viscositymineral oil containing a small amount of an oleophilic surface cationactive wettin agent.

4. A method of preventing further water abdue to sorption by undergroundbentonitic clay strata comprising the step of injecting thereinto a lowviscosity petroleum distillate containing a small amount of anoleophilic surface cation active wetting agent.

5. A method of preventing further water absorption by underground claystrata comprising the step of injecting thereinto a low viscositypetroleum distillate containing a small amount of an oleophilic surfacecation active wetting agent and an anion active agent.

tive wetting agent, said mineral oil having a viscosity between about 50and 500 seconds Saybolt Universal at 100 F.

"I. A method of preventing landslides due to water absorption byunderground bentonitic strata comprising the step of injecting into saidstrata a low viscosity mineral oil containing a small amount of paraiflnwax amines."

8. A method of preventing landslides due to water absorption by.underground bentonitic strata comprising the step of injecting into saidstrata a low viscosity mineral oil containing a small amount ofaquaternary ammonium compound having at least one saturated hydrocarbonchain of at least 8 carbon atoms. I

9. A method of preventing landslides due to water absorption byunderground bentonitic strata comprising the step of injecting into saidstrata a low viscosity mineral oil containing a small amount of asurface cation active amine having at least one aliphatic saturatedhydrocarbon chain of at least 8 carbon atoms.

10. A method of preventing landslides due to water absorption byunderground bentollitic strata comprising the step of injecting intosaid strata gas-oil containing a small amount of an oleophilic surfacecation active agent.

11. A method of preventing landslides due to water absorption byunderground bentonitic strata, which is in an incipiently dangerous condition due to a high water content, said method comprising the steps offirst treating said bentonitic strata with a substantially non-polarsolvent ior water to remove. at least a part oi said water in thebentonitic strata, and thereafter imecting into said strata alowviscosity mineral oil containing a small amount of an oleophiliccationic surface active wetting agent.

12. A method of preventing landslides due water absorption byunderground bentonitic strata, which is in an incipiently dangerouscondition due to a high water content. said method comprising the stepsof first treating said bentonitic strata with dioxane to remove at leasta part of said water in the bentonitic strata, and thereafter injectinginto said strata a low viscosity mineral oil containing a small amountof an oleophilic cationic surface active wetting agent.

13. A method of preventing landslides due to water absorption byunderground bentonitic 6. A method of preventing landslides due to waterabsorption by undergroimd bentonitic strata comprising the step ofinjecting into said strata, which is in an incipiently dangerouscondition due to a high. water content, said method comprising the stepsof first treating said bentonitic strata with dioxane to remove at leasta part ofsaid water in the bentonitic strata, and

thereafter injecting into said strata gas-oil containing a small amountof "parailln wax amine. vrc'roa a. nunmsnr.

strata a low viscosity mineral oil containing a small amount of anoleophilic surface cation ac-

